Any fool can destroy trees. They cannot run away; and if they could, they would still be destroyed,—chased and hunted down as long as fun or a dollar could be got out of their bark hides, branching horns, or magnificent bole backbones. Few that fell trees plant them; nor would planting avail much towards getting back anything like the noble primeval forests. During a man’s life only saplings can be grown, in the place of the old trees—tens of centuries old—that have been destroyed.

As a boy I had liked both drawing and physics, and I always abhorred the role of being a spectator. In 1908, when I was 15, I designed, built and flew a toy model airplane which won the then-famous James Gordon Bennett Cup. By 16 I had discovered that design could be fun and profitable, and this lesson has never been lost on me.

During my pre-college years I went on many trips with my father into the oil fields to visit their operations. … I puttered around the machine, electronics, and automobile shops while he carried on his business. Both of my parents are inveterate do-it-yourselfers, almost no task being beneath their dignity or beyond their ingenuity. Having picked up a keen interest in electronics from my father, I used to fix radios and later television sets for fun and spending money. I built my own hi-fi set and enjoyed helping friends with their amateur radio transmitters, but lost interest as soon as they worked.

I bet it would have been a lot of fun to work with Einstein. What I really respect about Einstein is his desire to throw aside all conventional modes and just concentrate on what seems to be the closest we can get to an accurate theory of nature.

I have a sense of humor; but over the years that sense has developed one blind spot. I can no longer laugh at ignorance or stupidity. Those are our chief enemies, and it is dangerous to make fun of them.

I took biology in high school and didn't like it at all. It was focused on memorization. ... I didn't appreciate that biology also had principles and logic ... [rather than dealing with a] messy thing called life. It just wasn't organized, and I wanted to stick with the nice pristine sciences of chemistry and physics, where everything made sense. I wish I had learned sooner that biology could be fun as well.

Is what you are doing fun? Of course, physics is also fun—indeed it is an enjoyable way of life. One reason physics is fun is that each element of progress transforms an area of ignorance into knowledge, but it also creates, as a by-product, an amount of new and additional ignorance in excess of that which was reduced to understanding. Thus, the volume of delicious ignorance we produce is ever-expanding, like our exponentially exploding universe.

Our most distinguished “man of science” was the then veteran John Dalton. He was rarely absent from his seat in a warm corner of the room during the meetings of the Literary and Philosophical Society. Though a sober-minded Quaker, he was not devoid of some sense of fun; and there was a tradition amongst us, not only that he had once been a poet, but that, although a bachelor, two manuscript copies were still extant of his verses on the subject of matrimonial felicity; and it is my belief there was foundation for the tradition. The old man was sensitive on the subject of his age. Dining one day ... he was placed between two ladies ... [who] resolved to extract from him some admission on the tender point, but in vain. Though never other than courteous, Dalton foiled all their feminine arts and retained his secret. ... Dalton's quaint and diminutive figure was a strongly individualized one.

Wheeler’s First Moral Principle: Never make a calculation until you know the answer. Make an estimate before every calculation, try a simple physical argument (symmetry! invariance! conservation!) before every derivation, guess the answer to every paradox and puzzle. Courage: No one else needs to know what the guess is. Therefore make it quickly, by instinct. A right guess reinforces this instinct. A wrong guess brings the refreshment of surprise. In either case life as a spacetime expert, however long, is more fun!

When I was 9, my parents gave me a Commodore 64, which was fun. At the time, the opportunity to program your own computer was easier than it is today. Today there are significantly larger barriers because of the complexity built into computing.

From address at a conference on Google campus, co-hosted with Common Sense Media and the Joan Ganz Cooney Center at Sesame Workshop 'Breakthrough Learning in the Digital Age'. As quoted in Technology blog report by Dan Fost, 'Google co-founder Sergey Brin wants more computers in schools', Los Angeles Times (28 Oct 2009). On latimesblogs.latimes.com website.
As quoted, without citation, in Can Akdeniz, Fast MBA (2014), 280.

His credo, given to a group gathered to honor his life achievements at an Archaeological Society of America. Quoted in Associated Press article, published for example, as 'Developer of Stobe Photo Process Dies', Ocala Star-Banner (6 Jan 1990), 4B. The meeting was described in the article as “recent” to the publication date.

In science it often happens that scientists say, 'You know that's a really good argument; my position is mistaken,' and then they would actually change their minds and you never hear that old view from them again. They really do it. It doesn't happen as often as it should, because scientists are human and change is sometimes painful. But it happens every day. I cannot recall the last time something like that happened in politics or religion.
(1987) -- Carl Sagan